May 1, 2014
01:00 PM (EDT)

News Release Number: STScI-2014-21

Hubble Astronomers Check the Prescription of a Cosmic Lens

May 1, 2014: If you need to check whether the prescription for your eye glasses or contact
lenses is still accurate, you visit an ophthalmologist for an eye exam. The doctor
will ask you to read an eye chart, which tests your visual acuity. Your score helps
the doctor determine whether to change your prescription.

Astronomers don't have a giant eye chart to check the prescription for natural
cosmic lenses, created by galaxy clusters. The gravity of these cosmic lenses
warps space around them, magnifying and
brightening the light from distant objects behind them. Without these lenses,
background objects would be too dim to be detected by even NASA's Hubble
Space Telescope. But how do astronomers know whether the prescription for
these zoom lenses, which tells them how much an object will be magnified, is
accurate? Astronomers using the Hubble telescope have discovered the next
best thing to a giant cosmic eye chart: the light from distant exploding stars
behind galaxy clusters.